In the northern part of Heilongjiang province in Northeast China, on quiet nights, a mysterious red velvet curtain sometimes appears in the vast sky. Just as people are filled with wonder, it suddenly transforms into a blue meadow. At times, it resembles a moving python, while at other moments, it looks like galloping horses; or it may seem like a great fire igniting in the mountains, with flashes of light resembling swords and banners changing shape. This bizarre spectacle in the night sky is known as the aurora.
On the night of June 18, 1982, around 10 PM, a similar aurora was observed in the western parts of Heilongjiang and Jilin provinces, as well as in Inner Mongolia and northern Hebei. In the northern sky, not far from the horizon, a half-moon-sized milky white light appeared, which gradually expanded into a fan shape towards the northeast. By about 10:15 PM, an arc of light formed, brighter at the edges and darker in the center, obscuring the stars within. The arc continued to expand, dimming, and by 10:30 PM, it reached its maximum size, covering about one-fifth of the sky, with stars becoming visible again within the arc. By approximately 10:50 PM, most of the light had disappeared, and by 10:58 PM, it was completely gone.
Auroras have also been seen in other parts of the world. The regions with the highest chances of witnessing auroras in the Northern Hemisphere include northern Alaska, northern Canada, northern Iceland, northern Norway, and the southern New Siberian Islands. In comparison, the chances of seeing auroras in northern Heilongjiang are less frequent than in these areas, mainly occurring around March and September, specifically during the spring and autumn equinoxes.
The aurora is one of the most spectacular natural phenomena on Earth, yet it possesses immense destructive power. During auroral outbreaks, the ionosphere can be severely disrupted, affecting the propagation of shortwave radio signals, leading to significant impacts on communication and transportation. For instance, a taxi driver in Alaska once received commands from a dispatcher in New Jersey during a period of intense auroral activity. Simultaneously, false images may suddenly appear on radar screens monitoring polar flights, triggering alarms. Additionally, the constantly changing auroras can induce strong currents in elongated conductors such as power lines, telephone lines, and oil pipelines. This induced current can cause severe corrosion in oil pipelines. In 1972, an aurora caused a 230,000-volt transformer in Colombia to explode, leading to a blackout of a high-voltage power line from Maine to Texas.
So, how is this dazzling and powerful aurora formed? Previously, scientists generally believed that high-energy charged particles from the sun, upon reaching the vicinity of Earth, would be captured and controlled by Earth's magnetic field. They spiral down along magnetic field lines towards the geomagnetic poles, colliding with the low-density upper atmosphere to produce light. Alternatively, solar phenomena such as sunspots, flares, and prominences, along with intense nuclear reactions occurring in the sun, release vast amounts of energy, propelling charged particles like protons and electrons into space. These charged particles, known as the solar wind, enter Earth's vicinity and, due to the geomagnetic field, concentrate near the geomagnetic poles at high altitudes. The various gas atoms and molecules in the upper atmosphere are excited by these charged particles, resulting in the light phenomenon. According to this explanation, auroras should appear in a point-like form above the magnetic poles. However, this is not the case; instead, auroras manifest as irregular elliptical bands in the polar regions. This discrepancy raises doubts about the previous general explanations, leaving further research necessary to uncover the truth.
